Purple heart

Identification and origin

Tradescantia pallida belongs to the spiderwort family, Commelinaceae. It is native to Mexico, especially the Gulf Coast region from Tamaulipas to the Yucatán, where it grows as a ground cover. It has since naturalized in many warm regions.

First described in 1911 as Setcreasea pallida, it was moved to the genus Tradescantia in 1975, but the older names Setcreasea pallida and S. purpurea are still widely used in the trade. The epithet pallida means “pale”: the wild form has rather dull, gray-green foliage tinged with purple. The plant grown almost everywhere is the cultivar ‘Purpurea’, sometimes sold as ‘Purple Heart’, with deep violet stems and leaves.

It is a creeping, trailing evergreen perennial 6–12 in tall, with stems that spread 12 in – 2 ft or more. These thick, fleshy stems are fragile: they snap easily when brushed, and they root at the nodes. The alternate, pointed, lance-shaped leaves are 3–6 in long and about 1 in wide; covered in pale hairs, they wrap around the stem at the base and fold into a trough shape.

From midsummer into fall, and sometimes in other seasons, small pink to lilac-pink flowers open at the stem tips between two boat-shaped bracts. Each one has three petals and bright yellow stamens, measures 0–2 in across, and opens only on the morning of a single day, but others keep following.

Light

Color depends directly on light. In full sun the foliage reaches its most intense violet; in part shade the plant still grows, but the leaves turn greener and the color fades. Outdoors, give it at least several hours of direct sun a day.

Indoors, set it in the brightest window you have. Behind glass, though, harsh afternoon sun can mark the leaves, so filtered light at that time of day is better. A plant that turns green and stretches out with widely spaced leaves is almost always short of light.

Watering

Its fleshy stems make it quite drought tolerant, but it also accepts frequent watering as long as water drains freely. During active growth, water moderately once the top 1–1 in of the potting mix feels dry, then empty the saucer.

In winter, and especially for containers brought indoors, cut back watering considerably: growth slows, and a soggy mix in cool conditions rots the roots. A hanging basket in sun dries out far faster than a pot in shade, so always check the mix first.

Potting mix

Choose a rich, peat-free, soil-based potting mix that stays slightly moist while draining well. In the ground it adapts to clay, loam, or sandy soils and to acidic through alkaline pH, as long as drainage is good; it also tolerates some salt.

During active growth, feed about once a month. For plants overwintered indoors, stop feeding until new shoots appear in spring.

Temperature

Like the other tropical and subtropical tradescantias, it is comfortable at 61–81 °F. It does not tolerate temperatures below 50 °F, so bring containers in well before the first frost rather than waiting for cold nights.

In the ground it is perennial in USDA zones 10a to 11b. In somewhat cooler but mild climates, the top can be killed back and the plant regrow from the roots in spring; elsewhere it is grown as an annual bedding plant or as a houseplant. It handles heat very well.

Repotting

In a container it grows fast and soon fills its pot. Repot in spring, as growth resumes, into a pot only slightly larger with a drainage hole, using a peat-free, soil-based mix. Newly rooted cuttings start out in a small pot no wider than 6 in.

Before bringing a container plant in for the winter, you can cut it back to make it more compact.

Pruning

Pinch the stem tips regularly for a dense, well-branched plant. After flowering, shorten the stems that have bloomed; otherwise the plant quickly turns leggy and spindly. Remove spent flower stems as they appear.

In beds, shelter it from strong winds that break the brittle stems. In warm regions, keep an eye on its spread: it travels easily and can become invasive in borders.

Propagation

Cuttings are the simplest method and almost never fail. In spring or summer, take a stem tip about 6 in long, cutting just above a node. Push at least one node into a light potting mix, or root the cutting in a glass of water before potting it up.

For more reliable rooting, cover the pot with a plastic bag and keep it in bright light but out of direct sun. When a gentle tug on the stem meets resistance, roots have formed: remove the bag gradually over several days so the young plant adjusts to room air. Cuttings can also be overwintered indoors, taking up little space, and planted out the following year. Clumps can be divided too; seed, on the other hand, is rarely an option because it is almost never available.

Common problems

• Foliage turning green, faded color: too little light.
• Long, bare stems: too little light, or no pinching and no cutting back after flowering.
• Broken stems: wind, foot traffic, or a plant that gets bumped; the pieces root easily.
• Rot at the base: soggy mix, especially in a cool winter.
• Damaged leaves after a cold snap: exposure below 50 °F.
• Pests: indoors, watch for scale insects, mealybugs, aphids, spider mites, and thrips; black vine weevil can attack the roots. Outdoors, slugs, snails, and caterpillars chew young shoots. The plant is, however, generally free of diseases.

The same symptom can have several causes: look at light, watering, temperature, and root health together before drawing conclusions.

Toxicity

Its toxicity is low but real, for people as well as for dogs and cats; the toxic principle has not been identified. All parts of the plant are involved. Eating it can irritate the mouth and stomach, and sap from the leaves and stems can cause redness, irritation, or contact dermatitis in sensitive people and in pets, although these reactions are uncommon. Wear gloves when pruning or taking cuttings, hang baskets out of reach of children and pets, and if any is swallowed, call your veterinarian or Poison Control.